The invention relates to processes and apparatus for removing coatings, and particularly to a process and apparatus for removing at least part of a coating from a predetermined portion of a photoreceptor.
In electrophotography, and particularly in xerographic copying machines, coated substrates such as photoreceptor belts or cylindrical photoreceptor drums are common. Photoreceptor embodiments include at least one coating of photosensitive material, which can be formed on the photoreceptor by known techniques such as immersion or dip coating.
The peripheral ends of a coated photoreceptor are used to engage with flanges in a copier's drive mechanism and/or to support a developer housing. If the developer housing rides on the coated area at one end of the drum, the coating material is rubbed off and contaminates various components in the machine such as the cleaning system and any optical exposure systems employed in the machine. Also, the coating can interfere with devices that are designed to electrically ground the drum by merely riding on the outer surface at one end of the drum. Thus, both the outer and inner peripheral ends of a photoreceptor must be free of coating material.
Conventionally, the ends of a photoreceptor are masked before coating to prevent them from being coated. In dip coating, the upper end of the photoreceptor drum might be kept free of coating material by orienting the drum vertically and dipping the drum into a bath of coating material to a predetermined depth. However, the coating formed over the lower end of the photoreceptor must still be removed, usually by mechanically wiping the lower end and/or by applying solvents to it. Chemical treatments can cause solvent droplets or vapor to contact the coating in regions that are not intended to be removed, reducing the quality of the resulting photoreceptor. In addition, the initial cost of the solvent, and cost of solvent recovery can be very high. Moreover, where the coatings may contain different layers of different materials, different solvents may be required to remove different layers. This adds to the complexity of removal of photoconductive coatings with the aid of a solvent because each layer has to be separately treated with different solvent. Furthermore, organic solvents have a limited useful life and can be hazardous to work with. Mechanical techniques for removing coatings are cumbersome, inefficient, and often produce photoreceptors of unacceptable quality.